The present invention relates to the field of the analysis of the quality of glazings, especially automobile glazings.
The present invention relates more particularly to a method for analyzing the quality of a glazing, comprising:                a step of generating a digital image of a test chart produced in reflection by the external surface of the glazing on the outside, the test chart exhibiting a pattern composed of a plurality of contrasted elements defining interface lines therebetween;        a step of computing quantities representative of the glazing on the basis of the image generated, the computation being performed by a processing unit; and        a step of comparing the values computed for the representative quantities with respect to reference values.        
WO-A-02/42715 describes a method for analyzing the surface of a glazing consisting in extracting, by digital processing and for each pixel of the digitized image, local phases in two directions. The variations of the local phases make it possible to compute variations of local slopes of the surface of the glazing so as to deduce therefrom variations of curvature or variations of altitude of the surface.
It is possible, by comparing the curvature variations of the glazing with reference values, to proceed to the choice of the rejection of the glazing.
Nonetheless, whereas this possible selection criterion does admittedly allow appraisal of the curvature and the altitude of the glazing, it does not necessarily allow appraisal of the esthetic quality of the image produced in reflection by the glazing. Indeed, the esthetics do not depend only on the geometry of the glazing, but also, for example, on the position of observation.
If it were attempted to use such a method to appraise the esthetic quality of the glazing in reflection, certain glazings would sometimes be rejected without, however, exhibiting actual esthetic impairment or vice versa.
Furthermore, with a method of this type, the values computed on the edges of the glazing are generally not reliable.
Finally, this type of method requires lengthy and irksome calibration.
WO-A-2007/115621 and U.S. Pat. No. 6,392,754 also describe methods aimed at measuring the shape of the surface of the glazing. These methods exhibit in particular the same drawback as regards relevance of the assessment of the esthetic quality of the glazing.